Heat-treatment method of rendering metals ductile



Apr. 3, 1923.

E. ROTH y HEAT TREATMENT METHOD OF RENDERING `METALS DUCTILE Filed Jan. 19

Patented Apr. 3, 1923.

1,450,734 ICE.

EMERY RQTH, OF CHICAGO, ILLINDIS.

HEAT-TREATMENT METHOD or RENDERING METALS DUC'rILE Application led January 19, 1921. Serial No. 438,331

To all whom t may concern.'

Be it known that I, EMERY ROTH, a citizen of Hungary, residing .at Chicago, county of Cook, State of Illinois, have invented a certain new and useful Improvement in Heat-Treatment `Methods of Rendering Metals Ductile, and declare the following to be a full, clear, and exact description of the same, such asv will enable others skilled in the art to which it pertains to make and use the same, reference being had to the accompanyin drawings, which form a part of this speci cation.

The present mvention relates more particularly to those refractory metals, metal mixtures, and alloys,.with or without nonmetallic additions, of which tungsten is an example, which can be formed into considerablel masses only from an agglomeration under suitable of the materials themselves or their comounds in powdered or granular form; the individual particles or grains being united pyressure, with or without the application of inders, into ingots or rods.

The object of the present invention is to produce pure refractory metals, mixtures and alloys of the same, with or without nonmetallic additions, in the form of comparah tively large masses which will be capable of being worked mechanically in a cold state, with possible occasional annealing, in the same manner as the ordinary so-called ductile metals and without requiring mechanical working such as rolling, swaging, drawing, etc., in order to secure ductility.

It is known thatv if gradually from a minimum temperature, at which no permanent structural change takes place, to a critical. temperature, at which the crystalline structure of the metal is permanently changed, orv above such critical temperature and close to the melting point of the metal, and then again gradually cooling the metal, the crystallization and the crystal growth can be directed at will. In thls way it is possible to obtain a single Ycristal or a multitude of elongated crysta iso over a considerable portion or the entire length of a heat treated rod or wire. The present invention is based on this princi le. I')I`he various features of novelty whereby m invention is characterized will herein- .after lbe pointed out with particularity in.

full understandin thefclaims; but, for a its ob]ects and a ofniy invention and of a metal is -heated R treated. The most important of such materials is tungsten and, for the sake of brevity, I shall confine the detailed description to the process of making ductile tungsten rods and ingots. This rod is formed in any known way of making rods of non-ductile tungsten. This rod is slowly passed through a comparatively short hot zone at a speed less than the speed of crystallization.l In the case of tungsten this hot zone should have a temperature of about three thousand degrees centigrade and the speed of travel of the rod through 'the zone should be about five meters per hour. Therod, which may initially be cool, is thus progressively heated from one end towardthe other, the portions which have passed through the heating zone cooling Gradually as other parts approach the heating zone. After the rod as been given the treatment just described, it is subjected to a nal heat treatment by passing through the same an electric current heavy'enough to heat the ingot to a high temperature which, inthe case of tungsten, should be about 3350 degrees centigrade. Both heat treatments should be effected in the presence of inert gases or inl a vacuum. eferring to the drawing, 1 represents the tungsten rod, the same being he d at its upper end in suitable Water-cooled jaws, 2, and dipping at its lower end into a mercury well, 3, surrounded by a cooling chamber, 4. Just above the mouth of the mercury well is an annular refractory member 5 whose outer and inner surfaces are both in the form of frustums of cones, the large end of the chamber within the refractory member being directed toward the mouth ofthe well. The refractory member is preferably made of tungstemand may conveniently be supported on tungsten posts, 6, rising from at and is connected at its other end to ak rod, '11; the rod, 11, being adapted to eX- into a suitable mercury trough, 15, resting on the table; the mercury serving to form a gas seal between the table and the bell and at the same time permitting the bell to be raised at will. The bell with its surrounding cooling chamber is held against lateral displacement and guided in its vertical movements by suitable vertical guide rods, 16, projecting upwardly from the table. The water-cooled jaw, 2, is supported on the lower end of a tubular member, 17,

= which passes out through the top` of the bell through a suitable stuffing box, 18. The member 17 serves not only as a support for the work but also as alconduit to permit 'the introduction of an inert gas under pressure. The table isprovided with a small opening, 19, extending through the same within the space enclosed by the bell, so that the inert gas may pass slowly outof the bottom of the chamber.

In starting the heat treatment, the tube, 17, is lowered so that substantially the entire rod or .ingot is submerged in the mercury. After the current has been on longenough to raise the temperature of the refractory member 5 to the desired point the tube 17 is slowly lifted so that one portion of the rod after the other is raised out of the mercury, brought into the heating zone, and then passes beyond the heating zone so as gradually to cool.

The nal heat treatment may be done in the treating or sintering bottles such as are now used in the manufacture of tungsten, but it can also be done in the apparatus which I have illustrated, the current being passed directly through the rod and being kept as uniform as possible because it has been found desirable to maintain uniform thermal conditions throughout this final heat treatment; Good results can be obtained by continuing this final heaty treatment for about the same length of time that it has heretofore been the custom to keep the work in the sintering bottles after it has gone through the various stages of mechanical workings and heat treatments heretofore deemed essential to the production of ductile tungsten, but I prefer to carry on this final heat treatment for considerably longer time' than heretofore.

i After the final heat treatment the rod or ingot will be found to be so ductile that it may be worked in a cold state in the same way as the s-called ductile metals, with only the occasional annealing that it is usually.

avoid inequalities in the heating of the rod, y

I have provided means whereby the annulus may be rotated as the rod is lifted. This may conveniently be accomplished by makingthe mercury well and its cooling chamber rotatable; suitable gearing, 21, being provided for this purpose, and the mercury well and its cooling chamber being supported at the lower end by a suitable step bearing ,22. A suitable stuffing box, 23, is

provided at the points where the well and its cooling chamber passthrough the table, this stuffing boX serving to prevent the escape of the inert gas within the well.

I claim:

1. The method of producing a comparatively large body of ductile tungsten which consists in forming a rod or long ingot of' non-ductile tungsten, passing it slowly through a short heating Zone having a temperature equal to or above the critical temperature at which the crystalline structure of the tungsten permanently changes and keeping that part of the rod or ingot which has not reached the heating Zone cool.

2. The method-of producing a comparatively large body of ductile tungsten which consists in forming a rod or long'ingot of non-ductile tungsten, passing it slowly through a short heating zone having a temperature of about 3000 degrees C. and, during this operation, keeping that part of the rod or ingot which has not reached the heating zonecool and permitting that part which has passed beyond the heating zone gradu ally to cool.

3. The method of producing a comparatively large body of ductile tungsten which` consists in forming a rod or-long ingot of v consists in forming a rod or long ingot of k tively large body of ductile tungsten which consists informing a rod or long ingot of non-ductile tungsten, placing the same in a mercury well, and raising it slowly out of the Well and `passing it through a short heating zone located above vthe Well and having a temperature of approximately 3000 degrees C. y

5. The method of producing a comparatively large body of ductile tungsten Which non-ductile tungsten, passing the same slowly throughan annulus heated to a tem-ff perature equal to or abovethe critical temcrystalline structure perature at which the of the tungsten permanently changes and, during this operation, keeping that part of the ingot which has not yet reached the annulus cool and permitting that part which as passed through the annulus gradually to cool.

6. The method of producing a comparatively large body of ductile tungsten which consists in forming a rod'or long ingot of non-ductile tungsten, lpassing the v same slowly to an annulus having an internal cross sectional area decreasing gradually in size in the direction of travel of the rod or ingot and heated to a temperature of about 3000 egrees C. and, during this operation, keeping that part of the ingot which has not yet reached the annulus cool and permitting that part which has assed through the annulus gradually to coo v permitting that part 7. The method of forming a comparatively large body of ductile metal from an agglomeration of small pieces of the metal or its compounds, which consists in pressing a mass of the material into a rod or long ingot, passing the rod or ingot slowly through a short heating zone having a temperature at or above the critical temperature at whichthe crystalline structure of the metal changes' permanently and, during this operation, eeping cool that art of the rod or ingot which has not reaclied the heating zone and which has passed said zone gradually to cool.

8. The method of forming a comparativelylarge bodyof ductile metal from an agglomeration of small pieces of the metal or its compounds, which consists in pressing a mass of the material into a rod or long ingot, passing the rod or ingot slowly through a short heating zone having va temperature at or above the critical temperature at which the crystalline structure of the metal changes 1 permanently and, during -this operation", keeping cool that part of the rod or ingot which has not permitting that part which has passed said Azone gradually to coolg'and afterwards heating the entire rod or ingot to a temperature considerably higher than that of the heating zone.

In testimony whereof, I sign this speci- EMERY RorH.

' cation.

reached the heating zone and 

